This invention relates in general to means for acquiring a communication link between two un-cooperating, optical transceiver systems, and in particular to such means which utilize reflecting telescopes.
While it is known that the use of a boresight mounted transmitter pair provides tight, secure communication with optical transmitter/receiver (transceiver) elements, such a configuration has problems in establishing boresight locking, tracking and search pattern techniques. U.S. Pat. Nos. 3,566,126 by Lang et al. and 3,511,998 by Smokler show the need for and problems associated with establishing two-way optical communication between remote, un-cooperating transceivers. Lang et al. presents a corner reflector at a first terminal to aid in acquisition of it by a second terminal in the absence of a transmitted signal from the first terminal. Smokler presents the use of separate frequency sets, f.sub.1 and f.sub.2, to distinguish between a stand-by mode (transmitting f.sub.1 and receptive to f.sub.2) and a call-up mode (transmitting f.sub.2 and receptive to f.sub.1). U.S. Pat. No. 3,504,182 by Pizzurro et al. presents optical tracking with non-coaxial optics and the use of a retro-reflector, but multiple wavelength light beams are used rather than multiple frequency communication modulation frequencies as used in this invention. U.S. Pat. No. 3,658,426 by Vyce presents the use of light pipes and retro-reflectors in measuring displacement of a remote object, with the light pipes (or fiber optic bundles) serving as a single, convenient optical pathway. Other optical communication systems either propose various tracking and communication systems, some with fiber optic omnidirectional detectors (U.S. Pat. No. 3,341,707 by Windfield), tracker schemes (U.S. Pat. Nos. 4,279,036 and 4,576,480 by Pfund and Travis, respectively), or optical pointing schemes (U.S. Pat. Nos. 4,330,204 and 4,603,975 by Dye and Cinzori, respectively). U.S. Pat. No. 3,504,979 by Stephany presents passive and active tracking using a retro-reflector or other types, such as a cat's eye, but due to optical limitations, the retro-reflector must be smaller in size than the cross-sectional area of the incident beam. U.S. Pat. No. 3,942,894 by Maier presents a pass-through optical system with a return reflection path for auto collimation with an input beam. This is just a local form of optical alignment with an incoming beam.
This invention utilizes a unique combination of multiple tapered fiber optics, dual boresighted telescopes with self-contained transmitter/receiver systems, and cat's eye reflector optics that provides a mechanically controlled boresight alignment precision that exceeds that of any previously presented systems. It also has the unique aspect that communication between transceiver sets only requires relative hemisphere location knowledge, and modest timekeeping accuracy.
Other advantages and attributes of this invention will be readily apparent upon a reading of the text hereinafter.